Sycorax

They appear to be skinless humanoids wearing mantles of bone, usually keeping their features concealed under helmets. They are proficient in the use of weapons like swords and whips, the latter which can deliver an energy discharge that disintegrates the flesh of its target. Their language is called Sycoraxic. The Sycorax also appear to have technology that is either disguised or treated as magic, referring to “curses” and the Doctor’s regenerative abilities as “witchcraft”.

The Sycorax leader referred to an “armada” that They could use to take Earth by force if the blood control failed. They also appear to have a martial society, with traditions of honourable combat.

The Tenth Doctor told Martha that The Sycorax survived the end of the universe, along with humans and another unidentified species.

In 1599, the Tenth Doctor, in the presence of William Shakespeare, noted how an animal skull reminded him of a Sycorax. (The Shakespeare Code)
The Great Intelligence mentioned, among others, the death of “the leader of the Sycorax” At The hands of the Doctor to dispute Madame Vastra’s claim that The Doctor was never “blood-soaked”. (The Name of the Doctor)